tonality: The term is usually understood to mean a harmonic system in which music is organized into major and minor keys. A conventional tonal piece, whether it be a movement of a symphony or an aria in an opera, is always centered on a particular key, such as C major or D minor. The harmonies may drift far from that key, but it is understood that the music will eventually return home. This kind of tonality flourished from around 1600 to 1900, whereupon it became one among many competing harmonic systems.Atonalitywas one alternative; but a large number of twentieth-century composers devised ways of working with tonal chords or characteristic tonal shapes without obeying the textbook rules of major- and minor-key tonality. Messiaen was particularly creative in this regard, with his system of modes of limited transposition.

tone row: See twelve-tone music below.

tonic: The root note of a scale. The tonic triad is the triad built on that note; for example, the C-major triad in the key of C. The close companion of the tonic triad is the dominant, built on the fifth note of the scale; in conventional tonality, it often leads back to the tonic, in a progression is called dominant-tonic (or V-I). Here is a dominant seventh chord on G followed by a resolution to C major:

total serialism: Any given note in a piece can be classified according to certain properties. What is the name of the note? How long does it last (duration)? How loud or soft is it (dynamics)? Is it high, low, or in the middle (register)? Is it played sharply, smoothly, or in some other style (articulation)? What rhythm is it a part of? What is the tempo of the section? Total serialism attempts to organize most or all of these variables along the lines of the twelve-tone method, arranging them in series of twelve or some other number and encouraging an orderly movement through the series. The system had a relatively brief vogue in the 1950s and early 1960s, in the music of Pierre Boulez, Karlheinz Stockhausen, Luigi Nono, and other European avant-garde composers. Milton Babbitt independently devised an analogous method in the United States after the Second World War. Here is the beginning of Boulez's Structures 1a:

In earlier times the tritone was called diabolus in musica, or “the devil in music,” because it was considered a disturbing sound to be avoided. In the Romantic era, the tritone became ever more fashionable as a signifier of dark, diabolical energies, as in the scene in Wagner’s Götterdämmerung where Hagen watches and waits for his chance at revenge:

tuning note: Orchestra players tune their instruments to the note A before a performance. The note is customarily given by the oboe.

twelve-tone music, twelve-tone method of composition, serialism: Arnold Schoenberg’s technique of organizing a work, movement, or passage around a fixed set of twelve non-repeating notes. The composer bases his or her melodic material on the intervallic relationships of the set or some subset, although the set itself need not appear as a melody. The set is also called a row, tone row, or series. One can also apply contrapuntal techniques of retrograde, inversion, and retrograde inversion — running the notes backward, inverting the intervals, or doing both at once. Twelve-tone writing is not necessarily the same thing as atonality; one can arrange the row in a way that the resulting music sounds tonal, as Alban Berg demonstrated in his Violin Concerto and Lulu. Here is the master twelve-tone row of Lulu:

white-key music: If you play consecutive white keys on a piano, you produce a C-major scale (no sharps or flats). The term also refers to music in a major key that uses only the notes of its parent scale. Copland’s Appalachian Spring, for example, begins with fifty bars of “white-key” A major, meaning that it is restricted to the seven pitches of the A-major scale: